The present invention relates generally to an IP multimedia subsystem (IMS) and next generation network (NGN), and more specifically to a communications system and method that conforms with the IMS/NGN architecture and incorporates an application service control function operative to integrate, control, and manage both session-based and non-session-based application services.
The IP multimedia subsystem (IMS) is a communications standard defined by the third generation partnership project (3GPP) that was originally developed to integrate services provided over cellular networks and the Internet. The development of IMS fostered the creation of the next generation network (NGN), which encompasses communications network architectures and technologies defined by the Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T). NGN is configured not only to integrate, control, and manage services provided over various types of communications networks, e.g., voice, data, video, and wireless networks, but also to provide blended services that allow significant interaction between the disparate voice, data, video, and wireless services.
The IMS/NGN architecture includes a service layer and a transport layer. IMS is implemented within the service layer, and comprises three primary service control functions, namely, a call session control function (CSCF), a home subscriber server (HSS), and an application server (AS). The CSCF is configured to perform session initiation protocol (SIP) call control signal processing. In general, the CSCF includes three types of SIP routing engines, namely, a proxy-CSCF (P-CSCF), an interrogating-CSCF (I-CSCF), and a session-CSCF (S-CSCF), which are operative to perform session signaling and control, and policy management and enforcement for NGN. The HSS includes at least one database containing user profile information, which can be accessed by the CSCF to authenticate and authorize users to receive requested application services. The AS is configured to host and execute the requested services. A resource and admission control function (RACF) and transport functions are implemented within the transport layer. The transport functions comprise access and core network functions, both of which can include quality of service (QoS) resources. The RACF couples the IMS service control functions with the QoS resources within the access and core network functions to control QoS over the respective networks via, for example, the reservation of resources, and admission and gate control.
A goal of NGN is to integrate, control, and manage application services provided over all types of communications networks such as voice, data, video, and wireless networks, etc. For example, NGN can control and manage a voice-over-IP (VoIP) application service using SIP call control signaling as follows. First, at a user terminal, a SIP INVITE message is sent to the CSCF in the service layer of NGN to request the VoIP service. Next, the CSCF communicates with the HSS to authenticate and authorize the user to receive the requested service. If the user is successfully authenticated/authorized, then the CSCF communicates with the AS to begin setting up a VoIP call. The CSCF then sends a message to the RACF in the transport layer of NGN to request the QoS resources required for the VoIP call. Next, the RACF communicates with the access network function to determine whether the requested resources are available, and, if so, to reserve and allocate the resources. The RACF then determines whether sufficient bandwidth is available on the access and core networks, and possibly one or more other networks, to allow a VoIP packet data flow to be established from the user terminal to a destination terminal. If sufficient bandwidth is available, then the RACF communicates with the access and core network functions to reserve and allocate the necessary bandwidth, and to perform other functions such as QoS marking, policing, priority handling, etc., for the VoIP flow. If the destination terminal is located within the network of another service provider, then the RACF can also communicate with a border gateway to perform QoS functions such as QoS marking, policing, priority handling, etc., at the network interface. Because such QoS marking, policing, priority handling, etc., can be performed on a “per application” and “per user” basis, guaranteed or differentiated QoS and/or differentiated service plans can be provided for NGN, thereby allowing charges for the sessions providing the respective services and plans to be calculated accordingly. It is noted that the generation of charging records within the IMS/NGN architecture is typically performed by the CSCF in the service layer.
One drawback of the above-described communications system is that it fails to make accommodations for application services that are not controlled using SIP call control signaling, and therefore do not require a session to be established to provide the respective service. Such non-session-based application services include audio/video streaming, peer-to-peer (P2P) telephony, P2P file sharing, P2P video streaming, and web content downloading. In general, service providers cannot provide non-session-based services with guaranteed or differentiated QoS, and instead typically provide such services as best-effort flows for application services that are not controlled using SIP call control signaling, even though a majority of multimedia applications do not explicitly signal using SIP or other resource control signaling mechanisms. Therefore, while a predominate amount of multimedia sessions are established in IMS and NGN networks without any session control signaling, they lack the service guarantees or differentiated QoS often needed for multimedia applications, such as P2P telephony or P2P video streaming.
In addition, it can be difficult at best for service providers to calculate charges for non-session-based application services that are commensurate with the value of the respective service. In some cases, application services may employ SIP call control signaling, but they may not be configured to signal to the IMS/NGN resource control elements within the network to which they are directly connected. Essentially, these application services fall outside the signaling domain of the network provider, but they may require multimedia services. Without a mechanism within the network to perform call control functions for these non-provider based SIP-compliant application services, they too will lack the service guarantees or differentiated QoS often needed for multimedia applications. The failure of the above-described communications system to make accommodations for such non-session-based services may also delay the widespread adoption of NGN services.
It would therefore be desirable to have a system and method that can be employed within the IMS/NGN architecture to enable the integration, control, and management of both session-based and non-session-based application services, while avoiding the drawbacks of conventional communications systems that conform with the IMS/NGN architecture.